1. Field of the Invention
The present invention relates to an arrangement for the detection of relative movements of two objects as well as a force and/or moment sensor which utilizes such an arrangement. The invention further relates to potential applications for the force and/or moment sensor.
2. Description of the Related Art
In the state of the art, both arrangements for the detection of relative movements of two objects as well as force and moment sensors are known in a plurality of designs.
DE 36 11 336 C2 discloses a force and torque sensor which measures all six possible force and torque components in the Cartesian coordinate system by means of strain gauges. The apparatus consists of two spoke wheels arranged one above the other with four spokes each and a total of 20 strain gauges which are wired with one another. The complicated design of the sensor leads to high material and construction expenses. In addition, the rigidity of the arrangement is limited, which excludes many, in particular, industrial applications.
From EP 0 240 023 B1 an optoelectronic arrangement accommodated in a plastic ball is known into which six components, i.e. three displacements and three angular rotations can be input simultaneously. The arrangement has the advantage of a simple design because does not need more than six measuring cells which are arranged at equal angular distances from one another in a single plane. Three measuring cells measure movements in one plane, and three other measuring cells measure movements perpendicular to this plane. The employment of optoelectronic measuring cells ensures reproducibility, reliability, and freedom from wear. On the other hand, however, the corresponding six displacements and angular rotations in Cartesian coordinates must be computed first by means of a microcontroller, which necessitates additional expenditures. Depending on the data word width processed by the microcontroller, rounding errors can also occur so that the precision of the resultant values is below the original measuring values.
The pre-filed, post-published DE 100 34 569.7 A1 discloses a device for the detection of relative movements of one object, which essentially utilises the optoelectronic arrangement from EP 0 240 023 B1. The device is suited, in particular, for the detection of high forces and torques as they frequently occur in industrial applications. For this purpose the device comprises an intermediate part from an elastomer or a cast resin, which is arranged between an input and an output flange. Although this device can already accommodate high forces and torques, no protection against overload is provided which can result in the destruction of the device, in particular of the optoelectronic arrangement. The intermediate part is subjected to the most severe wear. Nevertheless, no means is provided which informs the user on a potential failure of the intermediate part or compensates such a failure. Incidentally, this device has the same drawbacks as the arrangement known from EP 0 240 023 B1.
Further documents which do not claim to be exhaustive and which show the technical background of the invention are: DE 32 40 251 A1; DE 27 27 704; U.S. Pat. Nos. 3,921,445; 3,628,394.